The present invention is directed to valves, and in particular globe valves.
Globe valves are general purpose valves that have been successfully employed in numerous applications. One such application has been as instrument valves in high pressure fluid lines for fluids such as oil and gas. Because of the nature of the construction of a globe valve, serious accidents have occurred when they were being used as instrument valves in high pressure lines. These accidents have been caused by the inadvertent removal of the stem from the bonnet or the bonnet from the body when opening the valve. Because the pressures maintained in high pressure lines is in the order of 6,000 to 10,000 psi a release of fluid can easily result in injury. In fact, when the fluid is oil, explosions can occur.
To avoid these inadvertent removals of the stem and bonnet, the stems have been swaged to the bonnet and external releasable clamps have been used to secure the bonnet to the body. These measures have not proven completely satisfactory.
The swaging of the bonnet over the stem results in a one piece bonnet and stem assembly. This is not only undesirable from a cost standpoint but the success of this measure depends upon the quality of the swaging which has been known to fail.
The external releasable clamps are not fool proof, as there is no quarantee that the clamps will be reinstalled after disassembly and repair of one of these valves. In operation, a valve that has been reassembled without the safety clamps reinstalled, which has been known to happen, can still result in serious injury.
Although it is possible to design a valve such that the bonnet and the body are of a one piece construction, such a valve would be undesirable in that it would be impossible to replace worn packing or washers or to reseat the valve. Thus, instead of repairing a valve, the entire valve would have to be replaced.